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Spiro-OMeTAD single crystals: Remarkably enhanced charge-carrier transport via mesoscale ordering

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Science Advances  15 Apr 2016:
Vol. 2, no. 4, e1501491
DOI: 10.1126/sciadv.1501491
  • Fig. 1 Crystal growth, shape, and crystallography.

    (A) Schematic diagram of the crystallization process. (B) Confocal optical microscopy image of a spiro-OMeTAD single crystal. (C) Unit cell of the single-crystal structure of spiro-OMeTAD (the fluorene fragments are highlighted in yellow).

  • Fig. 2 Comparison of transistor characteristics between spiro-OMeTAD single crystals and thin films.

    (A) Transfer characteristics in the saturated regime for the single-crystal FET. (B) Output curve of the single-crystal FET. (C) Transfer characteristics in the saturated regime for the thin-film FET. (D) Output curve of the thin-film FET.

  • Fig. 3 Modeling of intermolecular charge transport.

    (A) DFT-ωB97X-D/6-31G** energies and wave functions for the HOMO (left) and HOMO-1 (right) levels of a molecular trimer extracted from the spiro-OMeTAD single crystal along the a direction. Lower panels: Illustration of the transfer integrals estimated for adjacent molecules in the trimer; the blue squares highlight the fluorene rings for which wave-function overlap has a major contribution to intermolecular electronic couplings (transfer integrals). (B) DFT-B3LYP/6-31G** valence band structure and density of electronic states (DOS) of the spiro-OMeTAD single crystal; the crystallographic coordinates of high-symmetry points in the first Brillouin zone correspond to Γ = (0,0,0), X = (0.5,0,0), Y = (0,0.5,0), Z = (0,0,0.5), M = (0.5,0.5,0), and R = (0.5,0.5,0.5).

  • Table 1 Key lattice parameters of the spiro-OMeTAD single crystal.
    Space groupCell length (Å)Cell angle (°)
    abcαβγ
    Triclinic P−1 (no. 2)13.6614.7217.2886.2368.9880.01

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/4/e1501491/DC1

    Single-crystal data file.

    fig. S1. Optical microscope image of the spiro-OMeTAD single-crystal FET device.

    fig. S2. Optical microscope image of the spiro-OMeTAD thin-film FET device.

    fig. S3. Transfer characteristic of lithium salt–doped spiro-OMeTAD thin films.

    fig. S4. Transfer characteristics of oxidized spiro-OMeTAD single crystals.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Optical microscope image of the spiro-OMeTAD single-crystal FET device.
    • fig. S2. Optical microscope image of the spiro-OMeTAD thin-film FET device.
    • fig. S3. Transfer characteristic of lithium salt–doped spiro-OMeTAD thin films.
    • fig. S4. Transfer characteristics of oxidized spiro-OMeTAD single crystals.

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    Other Supplementary Material for this manuscript includes the following:

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